A microsomal preparation from porcine aorta catalyzes the incorporation of mannose from GDP-(14C)mannose and GlcNAc from UDP-(3H)GlcNAc into lipid-linked saccharides and into glycoproteins. The lipid-linked saccharides formed from these two sugars include a series of lipid-linked oligosaccharides containing mannose and GlcNAc and differing from each other in the size of the oligosaccharide. In order to study these reactions in more detail, the particulate enzyme was treated with the detergent, Noridet P-40, to solubilize the glycosyl transferases. Both the enzyme which transfers mannose from GDP-mannose to dolichyl phosphate to form mannosyl-phosphoryl dolichol and the enzyme which transfers GlcNAc-1-phosphate from UDP-GlcNAc to dolichyl phosphate to form GlcNAc-pyrophosphoryl-dolichol were solubilized by this treatment and these two transferases were partially purified on DEAE-cellulose. The properties and requirements of these two enzymes were studied and both were shown to utilize dolichyl phosphate as acceptors. The enzyme which transfers mannose from GDP-mannose to N,N'-diacetylchitobiosyl-pyrophosphoryl-polyprenol to form the trisaccharide-lipid (man-Beta-GlcNAc-GlcNAc) was also solubilized and its properties were examined. Other glycosyl transferases are also being studied in this way.